All summer long, recreational fishermen find their way to Cape May, NJ, home port of the Porgy IV, a77-foot charter fishing vessel. Day after day, Capt. Paul Thompson and his crew take them down Delaware Bay or out into the Atlantic to catch one fish and one fish only: the summer flounder. The flat bottomfish with two eyes on one side of its head is “the most popular because it can be caught by anglers of all different skill levels,” Thompson said.

The delectable and not so elusive summer flounder is “the holy grail in the mid-Atlantic. It’s fairly easy and inexpensive to catch,” said Erling Berg, another Cape May fisherman. “You just need a pole, a line, a hook, and some bait, and you just drift across and hit them in the snout, because they’re lying there.”

Once nearly gone, they are lying there now in sufficient numbers thanks in large part to the Magnuson-Stevens Act, a law enacted in 1976 to drive foreign trawlers 200 miles from American shores and build up the U.S. fishing fleet, but also to prevent overfishing.

Within 15 years, it accomplished the goal of protecting the coastal waters for American fishermen. But conservation is a longer, ongoing challenge, with fish populations subject to a host of factors from ocean warming and other environmental changes, more sophisticated technology, and the fact that fishermen get better and better at finding fish and hauling them in.

But in an era of partisan bickering over so many issues and rising hostility to regulation, federal fisheries management “has been a resounding, bipartisan success story,” said Lee Crockett, director of Pew’s U.S. fisheries projects.

For more than a quarter century, Pew has been in the vanguard of efforts that helped persuade Congress to make the conservation provisions of Magnuson-Stevens stronger, first in 1996 and then in 2006.

The Magnuson-Stevens Act of 1976 has helped restore stocks of summer flounder in the mid-Atlantic.

“Thanks to the new catch limits, the United States has the best managed fisheries in the world,” said Pew executive vice president Joshua S. Reichert, who leads the environment group. “We have long supported science-based ocean conservation and there have been real successes. But the work in many ways is only just beginning.”

Magnuson-Stevens created an unusual public-private approach to managing fisheries, with eight regional fishery management councils covering the waters from Alaska to Florida to Maine, and in the waters off Puerto Rico, the U.S. Virgin Islands, Hawaii, Guam, and American Samoa. The councils set catch limits, allocate quotas, and decide when and where fisheries must be closed or curtailed, subject to the approval of the secretary of commerce. They must follow marine scientists’ advice and put in place catch limits and other restrictions to rebuild depleted populations in 10 years, if biologically possible.

The new Congress might revisit Magnuson-Stevens this year or next. Now the task is “to keep the law strong and to focus on entire ocean ecosystems rather than tackling fish species one by one,” Crockett said. “We also need to do a better job of eliminating or minimizing bycatch”—when turtles, seabirds, and fish and other marine life are killed or injured unintentionally by fishermen targeting other species.

One measure of Magnuson-Stevens’ impact came in 2012 in what the National Oceanic and Atmospheric Administration called “a historic milestone”: Catch limits were put in place for the last of 537 species managed by the regional councils, and a record six stocks were declared rebuilt, including summer flounder, Gulf of Maine haddock, and Alaskan snow crab. But 43 important stocks, including New England cod, South Atlantic red snapper, and Pacific cowcod, remain classified as overfished.

Scallops were once overfished in New England, but preservation measures have resulted in a lucrative fishery.

It’s tough to make a living these days catching cod off New England, a fish so important to Massachusetts since Colonial days that a wooden carving of the “sacred cod” still hangs in the State House. But the seabeds are again full of scallops, and out along the Pacific Coast fishermen are catching delectable lingcod once more.

Such successes have been the result of years of efforts on several fronts. For instance, from the beginning, the fishery management councils have been dominated by representatives of the fishing industry, both commercial and recreational. Although they were supposed to base judgments on the best scientific advice, when the scientists suggested a range of allowable catch limits, “they’d always pick the highest number and make a bunch of risky decisions,” Crockett said.

Since the 1990s, Pew has been engaged in efforts to monitor the work of the councils. Over the past five years, it has assembled teams based along the Eastern Seaboard, from New England to the Florida Keys, and along the Gulf of Mexico, and on the West Coast, in Oregon, devoted to ensuring that the conservation provisions of Magnuson-Stevens are implemented in the water. They attend each council’s meetings, weighing in on key issues. With Congress strengthening the law, science has even greater influence on decision-making.

The rebirth of summer flounder shows “that listening to the science works,” said Joseph Gordon, who manages Pew’s mid-Atlantic fisheries work. “And hard catch limits based on science have been a key to ending overfishing on federally managed fish stocks.”

Sometimes even hard limits can’t get the job done by themselves. Cod, fished for centuries in the cold waters off New England and Canada, have not recovered. The New England council reported signs of a comeback in 2008, but the numbers were down in its most recent look.

“What New England’s cod situation shows is that decades of severe overfishing cannot be fixed overnight,” said Peter Baker, director of Pew’s fisheries efforts in the Northeast. “It will take years and years to rebuild the vaunted cod fishery to its former glory. We believe we’ve turned the corner by ending overfishing. Time will tell if these stocks can make the arduous climb back to health.”

Scallops, overfished to the point of depletion in the 1990s, are now rebuilt, benefiting indirectly from measures to protect cod and haddock that left their beds undisturbed for long spells. The bigger scallops that fishermen such as Tye Vecchione of Chatham, MA are catching fetch $10 a pound at docks from Cape Cod to Cape May and have become one of the most lucrative U.S. fisheries.

Vecchione, who gave up cod fishing 10 years ago, gets a share of the catch reserved for small boats and catches 50,000 pounds a year in the summer and early fall. “Our day-boat scallops are the best of the best,” he said. “We used to fish year-round, and the scallops were $6 a pound and never as good.”

Erling Berg, who fished for 35 years and sits on the Mid-Atlantic Fishery Management Council, said the reason for this success is “not magic. To leave more fish in the ocean, allow that fish to spawn and build up the population. If you don’t catch them, they’ve got a chance to reproduce.”

Red snapper, another fish prized by recreational and commercial fishermen, is biting again in the Gulf of Mexico and to a certain extent in the U.S. South Atlantic, although both populations are far from rebuilt. The recovery plan for Gulf of Mexico red snapper projects that it will take until 2032 to fully rebuild that species.

“This is a fish on the road to recovery after decades of depletion, but it’s on a long, slow path,” said Holly Binns, who directs Pew’s fisheries work in the Southeast and U.S. Caribbean from her base in Tallahassee, FL. Red snapper can live longer than 50 years and don’t peak as spawners until they are 10 to 15 years old. “Until recently, most of the red snapper caught were 2 to 3 years old. Now, many of them are 5 to 7 years old. This illustrates the population is recovering, but still not fully healthy,” said Binns.

Fishing for red snapper is big business in the Gulf, where the commercial and recreational fishermen split the catch almost down the middle.

The South Atlantic Fishery Management Council in 2009 imposed a moratorium on red snapper fishing from North Carolina to the Florida Keys because the population had plummeted to less than 15 percent of what scientists said was a healthy level. Pew helped marshal public support for the moratorium, with the council receiving 32,000 comments. Now, with early signs of a turnaround, the council allowed red snapper fishing to resume for a limited time last September. The Gulf of Mexico fishery council dropped its catch limit from 9 million pounds in 2006 to 5 million recommended by scientists in 2008, but now it’s more than 8 million and rising.

Another fast-growing species that experienced a quick change of fortune is the lingcod, on the Pacific Coast from the Gulf of Alaska to Baja California. It is not actually a cod, but a groundling—but like cod it makes for mouth-watering fish and chips. It was among eight groundfish declared overfished in 1999 but was rebuilt by 2005, years ahead of schedule. There are still strict catch limits, and fishermen grouse that some areas teeming with lingcod are off limits to protect rockfish.

In Newport, OR, fisherman Dave Logsdon’s allowed share of lingcod is 400 pounds a month from May to November, which he catches in a single day on reefs 30 miles offshore. What he doesn’t sell dockside from his boat, Grace Elizabeth, is snapped up by two local restaurants at up to $4 a pound, four times what it used to fetch. “There’s a lot more lingcod than there used to be,” says Logsdon, who also fishes for salmon and tuna, “and the thing about lingcod is you usually get them when you go for them.”

The champions of fisheries management and conservation, the late Senators Warren Magnuson (D-WA) and Ted Stevens (R-AK), are no longer around to protect their legacy, and so far no one has emerged on Capitol Hill to take up their mantle. Some lawmakers from states or districts with strong commercial and recreational fishing interests have pressed at times for weaker regulation.

But court rulings have supported the regulators’ efforts. In 2000, the D.C. Court of Appeals overturned a rebuilding plan that NOAA said stood only an 18 percent chance of success. “Only in Superman Comics’ Bizarro world, where reality is turned upside down,” could that be considered likely to work, the jurists wrote. Now the odds that a rebuilding plan will prevent overfishing must be at least 50-50.

The Rise and Fall of Fish Stocks

Source: National Marine Fisheries Service

Factors other than too much fishing are also at work. Ocean warming and other environmental changes can play havoc with fish spawning. Biologist John Devore, a groundfish specialist with the Pacific council, says some El Niños in the 1990s caused some of the lingcod’s problems.

Nevertheless, it is a common refrain among fishermen that there are more fish in the sea—especially the prize catches—than scientists count and that show up in the government’s annual Status of the Stocks report to Congress.

Yet, the scientific methods are sophisticated and comprehensive. NOAA has ships that use sonar to count schools of fish, and the fisheries agency collects reams of data from commercial fishermen’s logbooks and dockside sales receipts. It pays biologists to go out on fishing vessels and observe what is caught. Observers logged more than 70,000 days at sea in 2009. The agency also surveys recreational anglers.

The latest government tally listed 43 stocks as overfished and 34 as still being caught faster than they can reproduce. But 31 stocks now have been fully rebuilt, and a scorecard used to measure the sustainability of key stocks has registered a 67 percent increase since 2000.

Whether it’s Vecchione’s fat scallops, Logsdon’s lingcod, or the 8 million pounds of red snapper that anglers were allowed to catch in the Gulf in 2012, there’s much for consumers, conservationists, and fishermen to savor.

It’s still a struggle to get everyone on board, however. Lawmakers from New England and New York have unsuccessfully pushed bills to weaken the 10-year fisheries rebuilding target and give the councils flexibility to stretch out the plans for years and perhaps decades, increasing the risk that stocks will ever be rebuilt.

But despite ongoing debate and attempts to weaken the law, Magnuson-Stevens has provided fishery managers with the mandate and tools to ensure the sustainability of the fisheries, giving the United States one of the best management systems in the world. “The worst thing we can do is walk away from the progress we have made,” Crockett said. “We must continue to have strong mandates and enforce them—after all, that’s why we have achieved the success we have.”

Christopher Connell, a former Associated Press reporter, is a Washington writer.